1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel having an improved structure that can increase the emission of secondary electrons.
2. Description of the Related Art
Plasma display devices are flat panel display devices that display a desired number, a letter, or a graphic on a surface facing a plurality of substrates. A plurality of discharge electrodes are formed on a discharge surface, and a discharge space is filled with a discharge gas and sealed. The discharge gas generates light in the discharge space when a discharge voltage is applied to the discharge electrodes. Then, an image can be displayed on the discharge surface by applying an appropriate pulse voltage to points where the discharge electrodes are crossing.
Plasma display panels can be divided into a direct current type and an alternating current type according to the types of the driving voltage applied to the discharge cell or into a facing discharge type and a surface discharge type according to the configuration of the electrodes.
A surface discharge type plasma display panel includes a front substrate, a discharge sustaining electrode pair that includes X and Y electrodes disposed on an inner surface of the front substrate, a front dielectric layer that covers the discharge sustaining electrode pair, a protective layer coated on a surface of the front dielectric layer, a rear substrate disposed facing the front substrate, address electrodes disposed on an inner side of the rear substrate, a rear dielectric layer that covers the address electrodes, a plurality of barrier ribs disposed on the rear dielectric layer, fluorescent layers of red, green, and blue colors coated on inner walls of the barrier ribs. A space formed by coupling the front substrate and the rear substrate is filled with an inert discharge gas.
In the plasma display panel described above, when an electrical signal is applied between the address electrode and the Y electrode, a discharge cell for light emitting is selected, and when an electric signal is alternately applied to the X and Y electrodes, a stationary or a moving image can be displayed by emitting visible light from the fluorescent layer coated in the selected discharge cell.
In a three-electrode surface discharge type plasma display panel, brightness of the panel is displayed by ultraviolet rays and visible light generated by the discharge through the transparent discharge sustaining electrode pair, the front dielectric layer, and the protective layer. Therefore, the electrodes must be designed in consideration of an opening ratio in the fabricating of panels, and an appropriate material for forming the front dielectric layer and the protective layer must be selected.
The protective layer prevents the front dielectric layer from colliding with ions and reduces a discharge voltage by emitting secondary electrons when the ions collide with the front dielectric layer.
However, a conventional protective layer leads to an increase in voltage and a reduction in brightness since the protective layer is formed of magnesium oxide having a low secondary electron emission coefficient. Therefore, a protective layer that can emit a large amount of secondary electrons in the discharge space and is sufficiently resistant to sputtering is needed.
Also, the opening ratio of the panel must be considered when the protective layer is formed of a material having a high secondary electron emission coefficient since the conventional plasma display panel is disposed on an inner side of the front substrate.